The present invention relates to radial-piston pumps, more particularly to radial-piston fixed-stroke pumps which are integrated within electric drive motors.
Integration of an electric drive motor and pumping mechanism is known in the art. Jones U.S. Pat. No. 1,926,444, incorporated herein by reference, discloses a compressor or pump combined with a motor. Jones recognizes as early as 1933 that "a structure wherein certain motor parts and those constituting the compressor, pump or the like, interact and are common to each mechanism constituting the novel unit" serves to further "compactness, durability, simplicity and maintain the cost of production and upkeep at a minimum." Voight U.S. Pat. No. 4,850,812, integrated herein by reference, also recognizes the benefit of "utiliz(ing) an integrated design in which the pump elements and motor housing are co-extensive with one another" for applications involving limited available space, such as in aircraft.
Other references of note which disclose integration of a motor with a pump or pump-analogue mechanism, incorporated herein by reference, are Smith U.S. Pat. No. 2,468,948; Taylor et al. U.S. Pat. No. 4,831,297; and, Matsushima Japanese Patent 62-7993. Smith discloses a motor-compressor design which is especially useful for refrigerator applications. Taylor et al. teach integration of a motor with a propulsion propeller for marine applications; this submersible design requiring no external shafting or gears is advantageous not only in terms of compactness and noise reduction but also in terms of decreased susceptibility to corrosion and electrical conductivity by ocean salt water. Matsushima discloses a rotary compressor integrated in the rotor of an electric motor; the compressor vane slides on the inner peripheral surface of an eccentric hole in the rotor, and the discharge passage is positioned in the rotor, in furtherance of reduction of noise and vibration, so as to counteract the imbalance attributable to the eccentric hole.
Noise, compactness, suitability for use in certain deleterious fluid environments and overall efficiency are thus seen as aspects of hydraulic systems and the like which have drawn the attention of designers for various applications. Many industrial applications are required to meet Occupational Safety and Health Administration (OSHA) environmental noise standards. Marine, aircraft and other applications have significant space considerations. Many applications of hydraulic systems involve operation in corrosive environments, such as ocean water, where corrosive fluids are pumped; typically the pump/motor combination is totally immersed within the fluid being pumped.